3.1.4 MDA reaction on 6-5 double bond of
Li+@C60:
In this section, we have spelled out the effect of Li+encapsulation on 6-5 MDA reactions. The formation energy of the initial
adduct, A16-5OL (Figure S2 )
is nearly 2.0 kcal/mol lower than that of neutral C60for this particular step. The activation barrier
(TS16-5OL) and enthalpy change for
R16-5OL formation are 20.9 and 12.9
kcal/mol, respectively, which are 5.5and 3.5kcal/mol lower and higher
than its uncharged counterpart. The third DA reaction has been initiated
from A26-5OL, which is 5.5 kcal/mol
more stable than R16-5OL. The
transition state, TS26-5OL(Figure S1 ), necessary for
R26-5Lformation, is 10.5kcal/mol
downhill than its neutral analogue. The exothermic nature of this step
is also noted from its corresponding enthalpy change (-17.5kcal/mol).
The adduct complex, A36-5L necessary
for the fourth functionalization is energetically 4.4kcal/mol more
stable than R26-5OL.The activation
barrier (TS36-5L) associated with
tetra-substituted P45-6L formation is
nearly 9.0 kcal/mol, lesser than its neutral analogue.
The net exothermicity corresponds to the overall reaction procedure is
-65.5kcal/mol.
Similar to the neutral C60, for
Li+@C60 also, the second DA reaction
is a synchronous process. However, both the third and fourth DA
reactions exhibit greater asynchronicity than the neutral analogues as
the difference of lengths between the two newly formed C-C bonds in the
TS becomes more than 1.0 Å.
Thus, from our computational analysis, it is evident that each step of
sequential 6-5 MDA reactions on
Li+@C60 is kinetically more feasible
and thermodynamically more attainable than neutral C60,
just like its 6-6 counterparts.